Obesity and lack of exercise linked to chronic pain

NEW YORK (Reuters Health) - It may not be surprising, but people who exercise at least one hour per week have a lower risk of troublesome back, neck, and shoulder pain, a new study shows.

The new evidence supports the possibility that obesity and physical inactivity play a role in a person's risk of developing chronic pain in those areas, said study co-author Dr. Paul Mork, of Norwegian University of Science and Technology in an email to Reuters Health.

Mork and colleagues followed more than 30,000 adults who participated in a large Norwegian health study. They recorded participants' body mass index (BMI) - a measure of weight related to height - at the start of the study, as well as how often they exercised, and then tracked them over the next 11 years.

The authors divided the participants into four categories based on how often they exercised, and four categories based on their BMI. They also looked at how many people in each category developed chronic neck, shoulder, and lower back pain.

Overall, 1 of every 10 people in the study developed lower back pain, and nearly 2 of every 10 developed shoulder or neck pain.

After taking into account participants' age, BMI, whether or not they smoked, and whether they did manual labor at work,

the research team found that men who were exercising 2 hours or more per week at the start of the study were 25 percent less likely to have lower back pain 11 years later, and 20 percent less like to have neck or shoulder pain, compared men who didn't exercise at all. And women who exercised at least 2 hours per week were 8 percent less likely to develop lower back pain than women who were inactive, and 9 percent less likely to develop neck and shoulder pain.

Weight, not surprisingly, also affected the risk of chronic pain later on. Obese men were almost 21 percent more likely to develop chronic lower back pain than men of normal weight, and 22 percent more likely to develop neck or shoulder pain. Obese women were also 21 percent more likely to develop lower back pain than women of normal weight, and 19 percent more likely to develop neck and shoulder pain.

Based on the results, Mork believes that even moderate physical exercise - just one hour or more per week - "can, to some extent, compensate for the adverse effect of being overweight and obese on future risk of chronic pain."

"Chronic neck and back pain are important to public health due to their substantial influence on quality of life, disability, and health care resources," Dr. Adam Goode from Duke University in Durham, North Carolina told Reuters Health by email. Goode, a physical therapist, was not involved in the study by Mork's group.

Back in the mid-1990s, a study from the Netherlands estimated that low back pain cost that country nearly 2 percent of its gross national product. In their new paper Mork and colleagues write that "just a small reduction in the incidence of chronic lower back pain would have a profound economic impact."

Because of the way it was designed, the Norwegian study can't prove that lack of exercise and being overweight actually caused people's chronic pain, or that regular exercise and a more healthy weight prevented it. It could be that the people who did or didn't have chronic pain are different in ways the study did not measure.

However, given the known benefits of exercise and maintaining a healthy weight, Mork believes that "community based measures aimed at reducing the incidence of chronic pain...should aim at promoting regular physical exercise and the maintenance of normal body weight."